Are fluid sims broken in Blender?

I've been experimenting for a while and the results are... variable. Also there's very frequent hangs. I gather that a lot of other people report similar things and resort to the FlipFluid addon.

Is it the case that the devs recognise that there's a viable alternative so don't focus on fixing the issues, or is it that they can't use the code because FlipFluid is private?

I can make a "cup of coffee", but when it comes to slightly larger scales with different effectors it all seems to go a bit temperamental - I've read the docs and lots of stackexchange, but there's something that's just not right about it.